This invention relates to a polymeric sheet or carrier capable of storing and delivering to a wash, corrosive laundry care additives. In particular, it relates to a storage-stable sheet for packaging laundry care additives which is soluble in aqueous and detergent solutions.
It has long been desired to provide a single vehicle adapted to permit prepackaging of desired amounts of laundry care additives and for delivering such additives to a washing machine or other laundry water by simply adding a package formed from that vehicle to the wash. Typical washing machine additives include corrosive bleaches, enzymes, fabric softeners, fabric conditioners, wrinkle-release additives, additives for imparting a specific feed (texture) or "hand" to fabrics and detergents. Since many of such additives are not compatible with the skin and become degraded during storage without suitable protection, there has been a continuing problem for storing such additives and for delivering them to a washing machine or the like.
It has been proposed to employ packages comprising water soluble bags containing detergents for laundry use. Such bags are particularly appealing for home use where a measured amount of laundry care additive, such as a bleach or detergent, may be added directly into a laundering machine without waste or mess. Such packages are intended to provide the required amount of laundry care additive for a single filling of that machine.
Until now, however, such packages or other delivery systems have not proved entirely satisfactory. The difficulties in fabricating satisfactory packages have frustrated the art for many years. Sheet material for carrying a laundry care additive must simultaneously satisfy many conflicting requirements. The material must form a self-supporting film which rapidly dissolves or disperses in wash water at temperatures typically from about 60.degree. F. to 140.degree. F.
It has been proposed, for example, in U.S. Pat. No. 3,322,674 to employ polymeric materials having water-solubilizing groups or hydrophilic groups for that purpose. Such dissolvable film forming materials, as poly (vinyl alcohol) or cellulosic derivatives, however, were found to be oxidized by and rendered insoluble by strong laundry care additives, such as chlorine bleaches. Accordingly, it has been proposed to employ a barrier coating on the inside surface of the laundry package to shield the packaging material from the chlorine bleach. However, such packets have not been satisfactory, since upon prolonged storage, the barrier coatings tend to crack or tear and permit the bleach to contact the packaging material. After prolonged contact, the packaging material is oxidized and becomes water insoluble and the chlorine bleach loses its activity.
Conventional solution polymers providing high water solubility and containing from 25-50% of alkali-soluble monomers were once thought to be unsuitable as laundry care packaging material. Films formed from such polymers are usually hygroscopic and, during storage at high relative humidity, tend to lose dimensional stability and become unduly tacky. In addition, at low temperatures and low relative humidity often encountered during storage, such films tend to become unduly brittle. Accordingly, rolls of tear off packages formed from such sheet material may not readily separate by tearing. Further, conventional water-soluble polymers often lose their flexibility, during storage at low temperatures of 0.degree. F. or lower. The present invention overcomes these difficulties and remains relatively stable during these conditions.
Other water soluble, film forming material, such as cellulosic materials, are not easily cast into sheets and are not readily heat sealable. Accordingly, it can be difficult and time consuming to economically utilize such materials.
It is, therefore, a primary object of this invention to provide a polymeric carrier in sheet form capable of retaining a pre-selected amount of a reactive laundry care additive, which carrier is inert and stable to said additive during storage. It is another object of this invention to provide a water-soluble carrier for delivering laundry additive which will dissolve or disperse readily in aqueous or detergent solutions at temperatures from about 60.degree. F. to about 140.degree. F.
It is a further object of this invention to provide a polymeric film which possesses sufficient strength to resist the rigors of mechanical packaging processes, but which retains sufficient flexibility to permit handling without premature rupture or disintegration. A sheet having such properties may generally be referred to herein as a self-supporting sheet.
It is a still further object of the present invention to provide a water-soluble polymeric film which resists the destabilizing effects of high humidity.
It is yet another object of the invention to provide a polymeric film which resists embrittlement at low relative humidity or at low temperatures.
It is an additional object of the invention to provide a laundry care sheet for retaining and delivering particulate bleaches to a laundry wash.
It is a further object of this invention to provide a water-soluble polymer having improved and superior stability in the face of corrosive laundry care additives.
Other objects of the invention will be apparent to those skilled in the art from a reading of the detailed description of the preferred embodiment of the invention.